At least 30 coal carriers are floating off China's coast unable to offload their cargoes because the traders that bought them cannot find customers to buy the commodity.

"The numbers of vessels that will run on demurrage at the expense of at least 10 Chinese coal traders who bought the cargoes from international trading companies and coal producers from the US, Colombia and Indonesia is expected to increase over the next few weeks, the sources said in interviews on the sidelines of the Coaltrans Asia conference in Bali, Indonesia," reports Platts.

The drop-off in demand, exacerbated by high inventories thanks to a mild northern hemisphere winter and a surge in US exports – because power stations in that country are switching to natural gas – have led to a collapse in thermal coal prices.

Coal for power generation at the port of Newcastle in Australia, the benchmark for Asia, were quoted at $91.25 a tonne on Friday, its lowest level since October 2010. Thermal coal hit a post 2008 financial crisis high above $140 a tonne in January last year.

In contrast to the sharp declines in coal for electricity generation metallurgical coal has managed to stay above $200 a tonne this year. Heavy rains in Australia at the start of last year drove the price briefly to $300 a tonne, but historically $200 and above translates to robust reward for coking coal miners.

After falling from $235 per tonne to $211 at the Vancouver port for export to Asia in the current quarter, it was reported on Tuesday that Anglo-American had inked a July-September quarterly contract for high-quality hard coking coal with a South Korean steelmaker at $225 a tonne.